"The lines start going at a crazy speed, I'm treated like a machine, not a person," one worker tells the programme. Another says: "They don't know how to speak English so they can't get work anywhere else. They shut their mouth and do the work."

Such experiences and views are far from unique, particularly for agency workers on so-called flexible contracts.

"You expect to work the whole week, but if an order gets cancelled or they don't have enough birds, you get a text message saying 'you're not going to be needed tomorrow. I'll tell you later when we're going to need you'" one of the workers interviewed complains.

The programme also reveals how some agency workers arrive at the processing plant only to find their shift has stopped, meaning they won't get a full day's pay. But because of the remote location some workers are forced to hang around in the canteen, waiting for the bus.

The company in question denies any wrongdoing and points out that the processing plant is unionised, and says that there is "parity" in pay between agency and permanent workers.

But the cases highlighted by Dispatches are just the tip of the iceberg. One ex-employee of another large poultry company in East Anglia recently described to me his experiences of the industry.

"They paid little. We worked overtime, six or seven days, yet the wage was minimum. It was far to go to the plant, around 30 miles one way, you had to cover fuel expenses yourself so there was little left from the wage," Romas, from Lithuania, told me.

"The work was organised very badly. You come in the morning and the production is frozen yet it was necessary for it to be defrosted. You have to touch it when it's so cold, work with ice, the hands get frostbite. I've ruined my health, now I'm disabled."

Romas described working on some of the production lines in the factory: "I worked in a fridge, I had to take boxes from the conveyer... It's impossible to keep up because there are around 80 different types of boxes. During the break people working in the fridge are sent to work in a hot room defeathering chicken, you get hot, covered in sweat, there's no place to change clothes... and then you are asked to return to the fridge, you get cold again..."

He also described what happened when he got ill: "I asked for a day off to go to the doctor and I was told that I had to inform the agency two months in advance... two months in advance I did not know I will get ill."

Similarly, an ex-employee from another poultry slaughterhouse told me workers at his plant were sometimes refused permission to take time off for important events like baby scans.

Perhaps even more seriously, according to the worker, there were cases of verbal bullying at the processing plant in question: "If the work was piling up then they'd be quite abusive verbally and use basically foul language towards you, and [be] quite intimidating to some people."

Disturbingly, I've heard many similar stories whilst investigating the UK poultry industry in recent months - as well as being told of a host of other bad practices and cases of exploitation on both farms and in factories.

Dispatches, which also investigates the bakery industry and fruit farming, blames the problems it uncovered on one thing - the big supermarkets' endless drive to cut prices whilst keep profits high.

Fiona Gooch, from the Traidcraft organisation, tells the programme: "When the supermarket puts the squeeze onto the supply chain, each stage of the supply chain passes it on to the next one until someone who doesn't have any power can't resist it. Because as we are driving down prices, people are being exploited."

And this, unfortunately, applies to just about every foodstuff you can imagine, not just poultry.